The use of copper interconnects in semiconductor devices may require a barrier layer to surround the copper interconnect to prevent Cu+ ions from diffusing into a silicon oxide dielectric, also called silicon dioxide or oxide. Copper diffusion into an oxide may give rise to various detrimental phenomena, which may include poisoning of an active device. Current barrier layers may include titanium (Ti), tantalum (Ta), and derivatives of these metals such as nitrides and carbides of these metals. Silicon nitrides and carbides are also being employed as effective barriers. One example of a silicon carbide barrier layer would provide a first silicon carbide layer, on which a thick oxide deposition is placed. Another silicon carbide layer is placed over the oxide deposition. Another oxide deposition is placed over the second silicon carbide layer. The silicon carbide acts as a barrier for copper diffusion.
To avoid increasing the dielectric constant of the oxide, barrier layers should be thin. Current methods of forming barrier layers may be too porous or may be difficult to control to provide a thin barrier layer or may not be sufficiently pure.
It would be desirable to create thin barrier layers that have a high purity and low porosity, which may be more effective as barrier layers.